Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$42.76	5.265%	$45.0113	$45.01	$45.00	$45.00
Purchase #2	$138.79	4.121%	$144.5095	$144.51	$144.50	$144.50
Purchase #3	$192.41	13.529%	$218.4411	$218.44	$218.45	$218.40
Purchase #4	$64.59	11.682%	$72.1354	$72.14	$72.15	$72.10
Purchase #5	$100.38	5.291%	$105.6911	$105.69	$105.70	$105.70
Purchase #6	$240.89	4.621%	$252.0215	$252.02	$252.00	$252.00
Purchase #7	$41.68	12.144%	$46.7416	$46.74	$46.75	$46.70
7 purchase totals =	$821.50		$884.5515	$884.55	$884.55	$884.40